import java.util.Scanner;

public class Main {
    public static int Fib(int n){
        if(n <= 3){
            return n;
        }else{
            return Fib(n-1)+Fib(n-2);
        }
    }

    public static void main(String[] args) {
        Scanner num = new Scanner(System.in);
        while (num.hasNextInt()){
            int a = num.nextInt();
            System.out.println(Fib(a));
        }
    }
}
